Electronic clock with low power consumption

ABSTRACT

An astable multivibrator, driven by a solar battery or other long-term current supply, pulses an electromagnetic stepping drive for intermittently winding up a coil spring which powers a mechanical clockwork. The spring, connected to its stepping drive via a one-way coupling permitting manual rewinding, has one end secured to a leadscrew and has its other end tied to a nut thereon so that the degree of unwinding is indicated by the axial position of the nut on the lead screw. When the spring has been tightened to a predetermined extent, the nut trips an electric switch or a lever to prevent overwinding by disconnecting the multivibrator, arresting the stepping drive or decoupling that drive from its load.

United States Patent. 1

Donner 541 ELECTRONIC CLOCK WITH LOW [21] Appl. No.: 111,264

[30] Foreign Application Priority Data 111 3,724,200 [451 Apr. 3, 1973FOREIGN PATENTS OR APPLICATIONS 12/1956 Germany ..58/41A 11/1948 Italy..58/40 Primary Examiner--Richard B. Wilkinson Assistant Examiner-E. C.Simmons Jackmon Attamey-Kar1 F. Ross 57 ABSTRACT An astablemultivibrator, driven by a solar battery or other long-term currentsupply, pulses an electromagnetic stepping drive for intermittentlywinding up a coil spring which powers a mechanical clockwork.

Jan. 30, Germany ..P The pring onne ted to tepping drive via a onewaycoupling permitting manual rewinding, has one [52] U.S. Cl. .58/41 R,58/83 end secured to a leadscrew and has its other end tied [51] Int.Cl. ..G0lc 9/00, G04b 9/02 to a nut thereon so that the degree ofunwinding is in- [58] Field of Search 58/23 R, 40, 41 R, 41 A, 41 B,dicated by the axial position of the nut on the lead 5 /46 43 3 screw.When the spring has been tightened to a predetermined extent, the nuttrips an electric switch [56] References Cied or a lever topreventoverwinding by disconnecting the multivibrator, arresting the steppingdrive or UNITED STATES PATENTS decoupling that drive from its load.

3,474,618 10/1969 Klinck ..58/41 R 21 Claims, 4 Drawing Figures Balancera Clockwork f/ Rafcher Coupling Sfepping Drive Pulse GeneratorPATENIEDAPM Inn 3.724200 SHEET 1 [1F 3 Balancer I Clockwork D forceSforer Follower s V f% I6--EE Oielrrfurfzning 14;. Ratchet "/P Couplingfife n Dr've 2 PP 9 Pulse Generator SOLAR BATTERY Z1 Z: Z: Zu 5m SiegmarDonner INVENTOR.

BY l Kw.

Allr'une y PATENTEDAPR 3 197a SHEET 3 [1f 3 The present inventionrelates to a clock or other timepiece with a long-term or regenerativeelectric power supply, such as a solar battery or a set ofairdepolan'zed cells.

Electrically powered timepieces of conventional design, using, forexample, a nickel-cadmium battery with a photoelectric circuit as acurrent supply, have various drawbacks including limited storagecapacity per unit of weight, poor efficiency requiring relatively longcharging periods, and a tendency to deteriorate beyond recovery uponprolonged discharge without recharging. Thus, photoelectricallyregenerated accumulators are particularly vulnerable to extended periodsof darkness or reduced illumination, e.g., when stored in vaults ortransported in crates, so that special precautions must be taken toinsure their operative condition upon subsequent exposure to light.

An object of the present invention, therefore, is to provide an improvedtimepiece of this general character which avoids the aforestateddrawbacks.

A more particular object is to provide means in such a timepiece forefficiently storing, over an extended period, the energy delivered by asolar battery or the like during times of abundant supply.

It is also an object of this invention to provide means for conservingthe available electric energy for extended periods.

These objects are realized, pursuant to the present invention, by theprovision of a mechanical force storer which powers the clockwork of thetimepiece and which is intermittently reloaded by a mechanism ineludingan electrodynamic stepping drive connected to an electronic pulsegenerator for periodic energization thereby. The mechanical force storeris provided with a follower which, whenever the force storer reaches apredetermined state of loading, trips a device for disconnecting thepulse generator from its power supply or otherwise blocking thereloading mechanism to prevent overloading. I

Even after protracted idleness, such a timepiece can be put into servicealmost immediately, either by regenerating its power supply or bymanually reloading its force storer pending such regeneration. The pulsegenerator may be an astable multivibrator, preferably consisting of twocascaded transistors of opposite conductivity type, which drawsvirtually no current during the intervals between pulses. The steppingdrive advantageously comprises an electromagnetic coil in series withthe second-stage transistor and a swingable armature in the field ofthat coil, the armature being preferably spring-loaded so as to have anatural frequency substantially coinciding with the operating frequencyof the multivibrator.

To translate the reciprocation. of the swingable annature intounidirectional rotation of a shaft, a one-way coupling such as apawl-and-ratchet drive may form part of a transmission linking thatarmature with the input end of the force storer. This one-way coupling,or a similar one such as an overrunning clutch in cascade therewith,allows the shaft to be manually turned by a key or the like to reloadthe force storer independently of its electrically powered steppingdrive.

The mechanical force storer is preferably a spring,

although a weight of the type used in pendulum clocks would also besuitable. In an embodiment preferred for its compactness, the spring isa spirally coiled band having one extremity secured to a leadscrewcentered on its axis and having its other extremity coupled with a nutriding on that lead-screw. If the pulse generator operates at its normalrate consistent with a charged supply battery, the input end of thespring is rotated more rapidly (in a tightening sense) than its outputend and the nut moves axially on the leadscrew until it trips theassociated blocking device. The latter may be an electric switchconnected as a circuit breaker in the input or in a feedback path of themultivibrator; it could also be a lever interposable in the path of theelectromagnetic armature or coacting with its stepping pawl to decoupleit from the associated ratchet, thereby minimizing the energyconsumption of the pulse generator.

The invention will be described in detail hereinafter with reference tothe accompanying drawing in which:

FIG. 1 is an overall block diagram of a system according to theinvention;

FIG. 2 is a partly diagrammatic, partly perspective view of a physicalmode of realization of the system of FIG. 1; v

FIG. 3 is a view similar to FIG. 2, illustrating another embodiment; and

FIG. 4 is a perspective view of a modified part of the system of FIG. 3.

Reference will first be made to FIG. 1 which shows the principalcomponents of a system embodying this invention. It comprises a d-cpower supply in the form of a solar battery Z, constituted by severalseries-connnected selenium cells 2, Z and a capacitor C', connectedthereacross. This power supply feeds an electronic pulse generator 1periodically energizing an electromagnetic stepping drive 2. The latterintermitten tly reloads, via a ratchet coupling 11 and an over runningclutch 15 in series therewith, a mechanical force storer 3 powering aclockwork 4 under the control of a conventional balancer 5. Atransmission 6 connects the clockwork 4 with a timepiece including aminute hand 7, an hour hand 8 and a clock face 9.

Force storer 3 also entrains a follower 10 designed to disable thereloading mechanism 1, 2, 11, 15 whenever the stored force reaches apredetermined maximum. As diagrammatically indicated, the deactivationmay be accomplishedthrough one or more of several blocking means 12 14,i.e., with de-energization of the pulse generator 1 via a switchingcircuit 12, immobilization of the stepping drive 2 by way of an abutment13 and/or disengagement of the ratchet coupling 11 with the aid of aninhibitor 14.

Finally, the transmission linking the stepping drive with the forcestorer 3 includes a shaft with an extension 16 which is normally drivenby the overiunning clutch 15 but can be independently rotated with thehelp of a suitable tool for a rapid loading of the force storer 3 torestart the clockwork 4 or to prevent its stoppage in the case offailing electric energy reserve.

FIG. 2 shows details of the elements broadly described with reference toFIG. 1.

The pulse generator 1 illustrated in FIG. 2 comprises a PNP transistor Tand an NPN transistor T in emitter joined through aresistor R to thebase of transistor T the latter has its emitter tied to the negativeterminal of source Z and its collector returned to the positive terminalof that source through an elec 'tromagnetic coil 17 forming part ofstepping drive 2. A

feedback path from the collector of the second-stage transistor T to thebase of first-stage transistor T comprises a condenser C in series witha resistor R this path also including conductors 12 terminating at anormally closed switch 68. Circuit 12 (indicated diagrammatically inFIG. 1) isfurther connected to the junction of a pair of high-ohmicresistors R R serially connected across power supply Z, C to bias thebase of transistor T to a value which would normally render thistransistor conductive, thereby unblocking the transistor T withconsequent energization of coil 17 by a pulse which is differentiated bythe condenser C and the resistor R to drive the base of transistor Tstill more negative; this results in instant saturation of bothtransistors. As the condenser C discharges, through coil 17' andtransistor T in series, the driving current for transistor Tdecreases'and the feedback of its positive-going collector potentialthrough condenser C to the base of transistor T rapidly cuts off the'two transistor stages. Thus, the duration of the pulse is determinedprimarily by the capacitance of condenser C and the resistance of coil17 whereas the recovery interval depends on the time constant ofimpedances C R The high value of resistors R R prevents any substantialdrain of battery Z in the 'nonconductive state of the transistors duringwhich the condenser C, is recharged at a rate determined by itspreferably high capacitance and the internal resistance of the battery.The illustrated multivibrator may begin to function with a voltagedifference of as little as 0.8 V across this condenser.

Coil 17 forms part of a solenoid with a core 18 having a bifurcate end24 articulated to a swingable arm 23 which is suspended from a mountingplate 19 by a pair of parallel leaf springs 25, a swing plate 22 and ajoint 21. Mounting plate 19 is connected with the clock housing, notshown, by a screw 20. Elements 18 and 2124 constitute an armature whichtogether with springs 25 defines an oscillatory system whose naturalfrequency should equal or at least approximate the repetition frequencyof multivibrator 1 for optimum energy transfer. Arm 23 carries across-pin 26 engaged by a pair of looped ends 28 of a U-shaped wire 27serving as a stepping pawl for a ratchet 29 which also coacts with aretaining pawl 30 in the form of a leaf spring depending from a fixedsupport 31. Ratchet wheel 29 is rigid with a pinion 32 drivinga gear 33which in turn entrains a pinion 34 in mesh with a gear 35, this geartrain forming part of a step-down transmission also ineluding a pinion36engaging a gear 37 which together with a ratchet 41 and a spring-loadedpawl 42 constitutes the overrunning clutch 15'. Ratchet 41 is keyed to ashaft 38 whose extension 16, also shown in FIG. 1,- has a squaretermination 43 engageable by a socket wrench.

Shaft 38 carries a pinion 39 meshing with'a gear-'40 which is anchoredto the outer end of a flat spiral spring representing the force storer3; the inner end of this spring is'fastened to a shaft 63 whose frontportion is threaded and mates with a nut 64 slidably entrained by a setof rods 65 (only two shown) which extend axially from gear 40. Shaft 63,acting as a leadscrew for nut 64, also has keyed to it a gear engaging,via gears 45 and 46, a pinion 47 on a shaft 48 whose front end carriesthe hub 49 of minute hand 7. A gear train 50, 51, 52, 55

transmits the rotation of shaft at a reduced rate to a sleeve 53 on thatshaft which is integral the hub 54 of hour hand 8. A further gear 56 onshaft 48 is in mesh with a pinion 57 on the shaft of a' sprocket wheel58 whose teeth are alternately engageable, in the wellknown manner, bydogs 59, 60 on a balancing wheel 61 rocking under the control of a hairspring (not shown) whose tension is adjustable by an arm 62.

The front end of nut 64, which represents the follower 10diagrammatically illustrated in FIG. 1, is beveled and, in an extremeoutward position of that nut, engages a pushbutton 67 of switch 68 tobreak the feedback circuit of multivibrator 1 through conductors 12.Such an interruption of the circuit, occurring when the spring 3 hascontracted to a predetermined extent,

prevents further triggering of transistor T so that the pulse generatorT T is disabled. It will be apparent that switch 68 could also beinserted elsewhere in the circuit, e. g., in the positive lead ofbattery Z ahead of its junction resistor R in which case even the smallleakage current through resistors R R would be stopped when the spring 3is fully wound.

The system of FIG. 3 differs from that of FIG. 2 only by the omission ofswitching circuit 12, 68 which has been replaced by a mechanical device13(also diagrammatically iridicated in FIG. 1) for stopping the swing ofarm 23. This device 13 comprisesa lever 70 with an end 69 projectinginto the path of nut 64 for downward'camming, against the force of arestoring spring 72, inthe limiting position of the nut; the oppositeend 74 of the lever, normally resting against a fixed stop 73, is thenraised into the path of a pin 75 projecting transversely from arm 23,this end being beveled at 76 to intercept that pin anywhere along itsstroke and to halt the motion of solenoid core 18 whereby coil 17 actsnearly as a pure inductance drawing mainly reactive current. Though themultivibrator 1 will continue to generate periodic pulses, its consumption of electric energy will be small.

As shown in FIG. 4, the device 13 may be replaced by another form ofmechanical inhibitor 14 (see also FIG. 1) designed as a lever arm 174normally extending below a stepping pawl 127 coacting' with a ratchetwheel 129; the oscillatory system is here shown as a disk 123 swingableon a shaft 119 under the control of a solenoid core 118 and of anassociated hair spring 125. The remainder of the assembly is identicalwith that of FIG. 3 and has not been illustrated. When the nut 64 (FIG.3) engages the proximal end of the lever, its extremity 174 movesupwardly to lift the pawl 127 into a disengaged position in which-itcannot step the ratchet 129. In view of the resonance between thisoscillatory system and the multivibrator, power consumption is againminimized under these conditions.

Other mechanical inhibitors operating on the same general principleinclude; for example, a permanent bar magnet carried on the arm 74 oflever 70 (FIG. 3)

to repel the solenoid core 18 when placed in an aligned positiontherewith. I

It has been found that a clock according to the inven-- tion can becontinuously operated in the presence of illumination of as little as llux with the use of a solar battery consisting of four selenium cellshaving each an effective area of about cm If the regenerative effect ofthe solar battery is temporarily insufficient to balance the energyconsumption of the load circuit, the pulses generated by multivibrator 1will be incapable of advancing the ratchet 29 (or 129) during everycycle but may do so after several cycles by progessively building up theswing of the oscillating armature; when illumination is thereafterintensified, normal stepping will be resumed.

During such normal stepping, the nut 64 is advanced axially outwardly(toward blocking device 67 or 70) as the spring 3 is progressivelytightened, thus storing enough energy for the next period of failingillumination. Uninterrupted clock operation, even during long winternights, is thereby assured.

Deactivation at the source, as described in connection with FIG. 2, willbe particularly suitable for clockworks whose drive springs 3 orequivalent force storers are designed to keep the movement runningwithout reloading for long periods (e.g., a month); the switch 68 thenadvantageously includes some delay means, such as a lost-motion linkage,causing it to reclose the circuit 12 in a position of the nut retracted(i.e., shifted to the left) with reference to the position of circuitopening.

On the other hand, a mechanical stop as shown in FIG. 3 or 4 will besuitable where the spring runs down relatively fast; the modification ofFIG. 4 is particularly advantageous with oscillating armatures of largemoments of inertia.

Though the follower-controlled deactivating devices shown and describedare primarily intended to prevent overload, an analogous constructioncould be used to cut off the accumulator during periods of prolongednonuse, i.e., upon relaxation of spring 3 to a predetermined extent, inorder to conserve electric energy. Such a system could permit even theuse of depletionsensitive power sources, such as nickel-cadmiumbatteries, though the utilization of a more efficient regenerablecurrent supply (e.g., a selenium-type solar battery) is preferred in anycase.

I claim:

. l. A timepiece comprising:

a clockwork provided with time-indicating means;

a mechanical force storer coupled with said clockwork for powering same;

reloading means for said force storer including an electronic pulsegenerator including an astable multivibrator and a stepping driveperiodically energized thereby;

a supply of electric current for said pulse generator;

follower means linked with said force storer for displacement dependentupon the degree of loading thereof;

and blocking means operable by said follower means in a predeterminedstate of loading of said force storer for deactivating said reloadingmeans.

2. A timepiece as defined in claim 1 wherein said multivibratorcomprises two cascaded transistors provided with a feedback path.

3. A timepiece as defined in claim 2 wherein said transistors are ofopposite conductivity type.

4. A timepiece as defined in claim 2 wherein said blocking meanscomprises a circuit breaker inserted in said feedback path.

5. A fimepiece as defined in claim 2 wherein said supply comprises arechargeable battery connected across said transistors and a capacitorin parallel with said battery.

6. A timepiece as defined in claim 5 wherein said battery consists ofphotoelectric cells.

. 7. A timepiece as defined in claim 2 wherein said stepping drivecomprises electromagnetic coil means in series with one of saidtransistors and a swingable armature in the field of said coil means.

8. A timepiece as defined in claim 7 wherein said blocking meanscomprises a mechanical stop interposable in the path of said armature.

9. A timepiece as defined in claim 7 wherein said reloading meansincludes a rotatable shaft and a one-way coupling between said armatureand said shaft.

10. A timepiece as defined in claim 9 wherein said one-way couplingincludes a pawl and a ratchet, said blocking means being operable todisengage said pawl from said ratchet.

11. A timepiece as defined in claim 9 wherein said shaft is providedwith an extension for manually loading said force storer independentlyof said reloading means.

12. A timepiece as defined in claim 7 wherein said armature comprises aspring-loaded member.

13. A timepiece as defined in claim 1 wherein said force storercomprises a windable coil spring and a leadscrew connected with one endof said coil spring, said follower means being a nut on said leadscrewentrained by the other end of said coil spring for axial displacementalong said leadscrew.

14. A timepiece as defined in claim 13 wherein said blocking meanscomprises an element trippable by said nut in a predetermined axialposition thereof.

15. A timepiece as defined in claim 14 wherein said element is anelectric switch.

16. A timepiece as defined in claim 14 wherein said element is a lever.

17. A timepiece as defined in claim 1 wherein said follower means isoperative to deactivate said reloading means in a position of maximumloading of said force storer.

18. A timepiece comprising:

a clockwork provided with time-indicating means;

a mechanical force storer coupled with said clockwork for powering same,said force storer comprising a windable coil spring, a leadscrewconnected to one end of said coil spring, and a nut on said leadscrewentrained by the other end of said coil spring for axial displacementalong said leadscrew;

reloading means for said force storer including an electronic pulsegenerator and a stepping drive periodically energized thereby;

a supply of electric current for said pulse generator;

and blocking means operable by said nut in a predetermined state ofloading of said coil spring for deactivating said reloading means.

19. A timepiece as defined in claim 18 whereinsaid blocking meanscomprises an element trippable by said nut in a predetermined axialposition thereof.

20. A timepiece as defined in claim 19 wherein said element is anelectric switch.

21. A timepiece as defined in claim 19 whel ein said element is a lever.

1. A timepiece comprising: a clockwork provided with time-indicatingmeans; a mechanical force storer coupled with said clockwork forpowering same; reloading means for said force storer including anelectronic pulse generator including an astable multivibrator and astepping drive periodically energized thereby; a supply of electriccurrent for said pulse generator; follower means linked with said forcestorer for displacement dependent upon the degree of loading thereof;and blocking means operable by said follower means in a predeterminedstate of loading of said force storer for deactivating said reloadingmeans.
 2. A timepiece as defined in claim 1 wherein said multivibratorcomprises two cascaded transistors provided with a feedback path.
 3. Atimepiece as defined in claim 2 wherein said transistors are of oppositeconductivity type.
 4. A timepiece as defined in claim 2 wherein saidblocking means comprises a circuit breaker inserted in said feedbackpath.
 5. A timepiece as defined in claim 2 wherein said supply comprisesa rechargeable battery connected across said transistors and a capacitorin parallel with said battery.
 6. A timepiece as defined in claim 5wherein said battery consists of photoelectric cells.
 7. A timepiece asdefined in claim 2 wherein said stepping drive comprises electromagneticcoil means in series with one of said transistors and a swingablearmature in the field of said coil means.
 8. A timepiece as defined inclaim 7 wherein said blocking means comprises a mechanical stopinterposable in the path of said armature.
 9. A timepiece as defined inclaim 7 wherein said reloading means includes a rotatable shaft and aone-way coupling between said armature and said shaft.
 10. A timepieceas defined in claim 9 wherein said one-way coupling includes a pawl anda ratchet, said blocking means being operable to disengage said pawlfrom said ratchet.
 11. A timepiece as defined in claim 9 wherein saidshaft is provided with an extension for manually loading said forcestorer independently of said reloading means.
 12. A timepiece as definedin claim 7 wherein said armature comprises a spring-loaded member.
 13. Atimepiece as defined in claim 1 wherein said force storer comprises awindable coil spring and a leadscrew connected with one end of said coilspring, said follower means being a nut on said leadscrew entrained bythe other end of said coil spring for axial displacement along saidleadscrew.
 14. A timepiece as defined in claim 13 wherein said blockingmeans comprises an element trippable by said nut in a predeterminedaxial position thereof.
 15. A timepiece as dEfined in claim 14 whereinsaid element is an electric switch.
 16. A timepiece as defined in claim14 wherein said element is a lever.
 17. A timepiece as defined in claim1 wherein said follower means is operative to deactivate said reloadingmeans in a position of maximum loading of said force storer.
 18. Atimepiece comprising: a clockwork provided with time-indicating means; amechanical force storer coupled with said clockwork for powering same,said force storer comprising a windable coil spring, a leadscrewconnected to one end of said coil spring, and a nut on said leadscrewentrained by the other end of said coil spring for axial displacementalong said leadscrew; reloading means for said force storer including anelectronic pulse generator and a stepping drive periodically energizedthereby; a supply of electric current for said pulse generator; andblocking means operable by said nut in a predetermined state of loadingof said coil spring for deactivating said reloading means.
 19. Atimepiece as defined in claim 18 wherein said blocking means comprisesan element trippable by said nut in a predetermined axial positionthereof.
 20. A timepiece as defined in claim 19 wherein said element isan electric switch.
 21. A timepiece as defined in claim 19 wherein saidelement is a lever.